The present disclosure relates generally to cosmetic and dermatological formulations containing peptides that improve the appearance of skin, reduce or inhibit environmental damage to skin, or some combination of these.
Ultraviolet radiation (UV) is a major causal factor for skin (cutaneous) aging. It's been reported that repeated exposure to ultraviolet radiation (e.g. sunlight) can cause the skin to age prematurely, a condition which has been termed “photo-aging” (John J. Voorhees, New England J. Med, Nov. 13, 1997). Photo-aged skin can be characterized by wrinkles, presence of brown spots, changes in pigmentation and/or surface roughness. These changes are not part of the natural, normal aging process of the dermal tissue. In addition, exposure to environmental factors such as smog, consumption of alcohol, tobacco, and stress can also lead to pre-mature aging of the skin. Furthermore, inflammatory response associated with various skin injuries (e.g. cuts, burns) and dermatological conditions (e.g. skin infections, acne) can also contribute to pre-mature skin aging.
The cosmetic industry is continuously searching for novel ingredients to counter the adverse effects of premature skin aging as well as ways to reduce undesirable effects associated with skin inflammation where possible. Thus, it is desirable to have novel cosmetic and/or dermatological compositions to counter conditions associated with pre-mature skin aging.
General Aspects of UV And Free Radical Induced Skin Aging
There are a variety of causal factors for accumulated cellular damage in the skin that lead to premature skin aging. Among these are the oxidative processes and related free radical damage that result from UV lights (e.g. sunlight), smog, toxins, cigarette smoke, X-rays, drugs, and other environmental stressors. Although sunscreens can be used to reduce skin cancer and sunburn, they may not fully protect against skin photo-aging, since sunburn and photo-aging can be caused by different types of ultraviolet (e.g. UVA, UVB, UVC) light as well as damages arising from certain UV induced reactive oxygen species
Typically, when skin is exposed to these potentially damaging changes, there is sufficient cellular energy adenosine triphosphate (ATP) for cellular repair and/or renewal. However, as an individual ages, enzymes that provide antioxidant activity such as superoxide dismutase (SOD) and catalase become less available, leading to decrease in antioxidant enzymes to combat free radicals, reactive oxygen species, and/or peroxides. Organs such as the hands, face, neck, and arms are areas usually chronically exposed to light and this continuous exposure to sunlight can lead to generation of free radicals in the dermal layer.
Certain dermal components are especially susceptible to free radical induced oxidative stress or the concomitant and/or subsequent inflammatory alterations in the dermis. The skin protein collagen is particularly susceptible to free radical damage and the resultant cross-collagen linking. Collagen cross-linking can be characterized by the transition of normally elastic/mobile collagen to become stiff and less elastic/mobile. The result is an aging appearance (e.g. wrinkles) and reduced tonicity in the skin. In addition, presence of acne has also been linked to free radical/peroxide production.
It is well recognized in the art that antioxidants are able to donate an electron to a free radical, stabilizing the free radical and stopping the chain of chemical reactions and potential damage. In a similar manner, antioxidants can prevent free radical damage which can slow the aging process.
The survival of embryonic motoneurons has been found to be dependent upon specific trophic substances derived from the associated developing skeletal muscles. Certain skeletal muscles have been reported to produce substances that are capable of enhancing the survival and development of motoneurons by preventing the embryonic motoneurons from degeneration and subsequent, natural cellular death. These substances have been broadly described as neuronotrophic factors (NTFs), which are a specialized group of proteins which function to promote the survival, growth, maintenance, and functional capabilities of selected populations of neurons (e.g., Chau et al., 1990, Chin. J. Neuroanat. 6:129).
U.S. Pat. No. 6,309,877, U.S. Pat. No. 7,183,373, U.S. Pat. No. 6,841,531, U.S. Pat. No. 6,759,389 and US20060052299 disclose motoneuronotrophic factors (MNTFs), which are peptides that exhibit trophic effects on motoneurons.